Avoparcin is an important, commercially available, antibiotic which is used in the feed of meat-producing animals to accelerate their growth rate. This antibiotic is generally prepared by a fermentation process and consists essentially of two water-soluble glycopeptides, hereinafter referred to as the alpha and beta components of avoparcin. These components are discussed in the following publications: W. J. McGahren, et al., Structure of Avoparcin Components, Journal of the American Chemical Society, 102, 1671 (1980) and Avoparcin, Journal of the American Chemical Society, 101, 2337 (1979).
When employed as an animal feed additive, avoparcin has generally been administered to said animals, in or with their feed, in the form of an alkyl sulfate complex associated with the dried solid of the whole harvest mash, or biomass, in which it was produced. In practice, this product has been obtained by a process involving, (1) acidification of the antibiotic containing biomass, from the fermentation process; (2) treatment of the acidified mixture with filter aid and alkali metal alkyl sulfate; (3) filtration of the thus treated acidified mixture and (4) drying of the recovered solids which comprise: avoparcin alkyl sulfate complex, filter aid, and biomass. Although the thus prepared product has been utilized effectively for acceleration of the growth rate of animals for nearly a decade without report of any undesirable side effects or toxicity problems, the relatively low potency of this biomass containing product limits, to some extent, the marketability of the antibiotic and the physical forms in which it may be administeeed.
Although the art suggests that avoparcin alkyl sulfate complexes can be obtained in a finished form free of mycelia, unfortunately, the art processes when scaled up to provide the volume of avoparcin alkyl sulfate complex needed by the meat-producing industry are not entirely satisfactory. They are limited by extended filtration periods and consumption of considerable amounts of energy and/or fuel necessary to achieve the degree of drying necessary to provide a dry stable product. Additionally, the physical form and appearance of the avoparcin alkyl sulfate complex produced by the scaled up art process leaves something to be desired.
In general, prior art processes of commercial significance are limited in that the concentration of the active ingredient in the product is limited by the nature of the process and the present state of the fermentation art. The maximum potency of the product which is currently achieved, is in the range 17% to 18%. The concentration of the active ingredient in the product is entirely dependent on the fermentation mash feedstock to the processes and will inevitably vary significantly from batch to batch. It is difficult to specify and quantify the many components, other than the active ingredient, which are present in the products as manufactured by the current processes. Furthermore, both the nature and the relative concentrations of these components will vary from batch to batch. Additionally, the physical and chemical properties of the product as currently produced, imposes major limitations on the types of supplement formulations which can be prepared. U.S. Pat. No. 4,485,102 describes nn improved method for the isolation of avoparcin alkyl sulfate complex of increased potency by adsorption and removal of some of the impurities on a sorptive medium which does not retain the antibiotic.
It is an object of this invention to provide high potency biomass-free avoparcin and a method for its preparation.